add localisation support

currently only en_GB (TODO: dynamic language pack imports)

src/lib/ui/post/BoostContext.svelte

@@ -1,5 +1,8 @@
 <script>
     import { shorthand as short_time } from '$lib/time.js';
+    import Lang from '$lib/lang.js';
+
+    const lang = Lang('en_GB');
 
     export let post;
 
@@ -9,10 +12,10 @@
 <div class="post-context">
     <span class="post-context-icon">🔁</span>
     <span class="post-context-action">
-        <a href={post.account.url} target="_blank"><span class="name">
-                {@html post.account.rich_name}</span>
-        </a>
-        boosted this post.
+        { @html
+        lang.string('post.boosted').replaceAll('%1',
+        `<a href={${post.account.url}} target="_blank"><span class="name">${post.account.rich_name}</span></a>`)
+        }
     </span>
     <span class="post-context-time">
         <time title="{time_string}">{short_time(post.created_at)}</time>
@@ -41,8 +44,8 @@
         margin-right: 4px;
     }
 
-    .post-context a,
-    .post-context a:visited {
+    :global(.post-context a),
+    :global(.post-context a:visited) {
         color: inherit;
         text-decoration: none;
     }